1. Field of the Invention
The present invention relates to a lithography process in a series of manufacturing processes of a semiconductor device, particularly to a managing method of an exposure apparatus for use in an exposure process of transferring a mask pattern, a managing method of a mask, an exposure method, and a manufacturing method of a semiconductor device.
2. Description of the Related Art
In general, a plurality of the exposure apparatuses is used to carry out an exposure operation in a lithography process. For the exposure apparatus, same exposure characteristics have to be ideally imparted even among a plurality of the exposure apparatuses, but actually a difference is generated among the exposure apparatuses. Therefore, even when the exposure apparatuses having same specifications are used to carry out an exposure operation, a difference is generated in finish of a pattern.
A typical example of the difference of the exposure characteristic is distortion generated while a projection/exposure process is carrying out. When the distortion is generated, a deviation is caused between standard grid coordinates and actual exposure coordinates within an exposure area. An amount of the deviation is generally about 20 to 30 nm, but an amount or a direction of the distortion differs among the individual exposure apparatuses. Therefore, for example, on an occasion of a superposition exposure is performed, even if the amount of a deviation of the superposition exposure can be set to 0 at a center of an exposure area, an error of the superposition exposure is generated in a whole of the exposure area in most cases.
To solve such a problem caused by distortion which occurs in carrying out the exposure operation by using the plurality of exposure apparatuses, for example, the following methods have been tried. First, the amount of distortion of each of the plurality of exposure apparatuses are compared with one another. Next, the exposure apparatuses are grouped so as to comprise a group of one or more exposure apparatuses, whose distortion amount differences are within a predetermined permissible range. Then, in a patterning process, the exposure operation is carried out using the exposure apparatus in the group whose distortion amount satisfies a desired permissible value. Details of a typical example of the exposure method are described in Japanese Patent No. 3104636.
When a plurality of exposure apparatuses are used, the problem concerning the deviation of the superposition exposure by the distortion difference among the respective apparatuses has gradually been improved by enhancement of capabilities of the exposure apparatus and enhancement of a control method. However, in recent years, it has been clear that causes for generation of a dimensional error of a resist pattern among the plurality of exposure apparatuses are not limited to the deviation of the superposition exposure by the distortion differences among the respective apparatuses, and other various causes also exist.
For example, with miniaturization of the resist pattern, there is hardly a difference between a resolution theoretical limit value of an optical system of the exposure apparatus and a dimension value of the actually formed pattern, and a dimensional precision of the pattern has been largely influenced by a small error of the optical system. The precision of the pattern itself required for forming the resist pattern having a micro dimension also needs to be high. Concretely, for example, when the resist pattern having a line width of about 110 to 130 nm is formed, the dimensional precision is necessary to such an extent that the error in the exposure area is about 10 nm or less, but it is very difficult to satisfy this precision. A main cause for this lies in that a manufacturing error is included in the line width of the mask pattern formed in a reticle (mask). However, even when the mask including an ideal mask pattern formed without any error is charged as such into the exposure apparatus to carry out the exposure, it is almost impossible to secure the above-described dimensional precision because of a transfer error of the exposure apparatus itself.
That is, the dimension of the resist pattern fluctuates because the exposure apparatus includes an error from an ideal state. When dimensional error factors such as illuminating a, numerical aperture NA of a lens, illuminance, astigmatism, and spherical aberration change in the exposure area, the dimension of the formed resist pattern also changes. With respect to the dimensional fluctuations of the resist pattern, these dimensional error factors independently exert influences in some cases, and exert interactions and influences in other cases. Moreover, the exposure apparatus of a semiconductor manufacturing apparatus is designed and adjusted beforehand so that the pattern can be transferred up to the resolution limit of the optical system. Therefore, a change amount of each dimensional error factor described above is extremely small. It is therefore very difficult to further reduce the dimensional error factor itself or to constantly hold the dimensional fluctuation of the resist pattern in the surface of a wafer (resist film).
Moreover, when the dimensional error of the resist pattern exceeds the permissible range, it is difficult to form various micro semiconductor elements to be incorporated in a semiconductor device in appropriate states. Additionally, there is possibility that quality or yield of the whole semiconductor device drops.